Huh. You made me think: I belong to a group that has a very tight-knit community and also a greater-than-average lifespan (Mormons). However, as far as I know (I haven&#8217;t done any research on this) the lifespan increase can be tied to the healthy behavior which is reinforced by belonging to the community (no smoking, drinking, drugs, etc.) &#8211; so I am willing to believe that tight communities foster healthy behaviors, and probably make people happier which also increases lifespan, but you&#8217;d have to do more work to convince me that the community itself did something directly.